Postretirement Benefits (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended
	Mar. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans		$ 92		$ 84	$ 198	$ 199
Expected full year contributions to pension and other postretirement benefit plans during the year		610			610
U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost		29		29	58	59
Interest cost		131		130	262	259
Expected return on plan assets		(183)		(189)	(367)	(378)
Amortization of prior service cost / (credit)		0		0	0	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits		(23)		(30)	(47)	(60)
Curtailments, settlements and termination benefits		0	$ 9	0	9	0
Total cost (benefit) included in operating profit		(23)		(30)	$ (38)	$ (60)
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost					4.20%	4.50%
Discount rate used to measure interest cost					3.30%	3.40%
Expected return on plan assets (as a percent)					6.70%	6.90%
Rate of compensation increase (as a percent)					4.00%	4.00%
Non-U.S. Pension Benefits
Components of net periodic benefit cost:
Service cost		24		23	$ 47	$ 46
Interest cost		25		30	50	60
Expected return on plan assets		(56)		(59)	(113)	(117)
Amortization of prior service cost / (credit)		(1)		0	(1)	0
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits		(8)		(6)	(17)	(11)
Curtailments, settlements and termination benefits	$ 20	0		0	20	0
Total cost (benefit) included in operating profit		(8)		(6)	$ 3	$ (11)
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost					2.30%	2.90%
Discount rate used to measure interest cost					2.30%	2.80%
Expected return on plan assets (as a percent)					5.90%	6.10%
Rate of compensation increase (as a percent)					4.00%	3.50%
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost		20		21	$ 39	$ 41
Interest cost		32		32	65	65
Expected return on plan assets		(9)		(11)	(18)	(22)
Amortization of prior service cost / (credit)		(6)		(15)	(11)	(30)
Net periodic benefit cost (benefit), excluding curtailments, settlements and termination benefits		37		27	75	54
Curtailments, settlements and termination benefits		0		0	0	(2)
Total cost (benefit) included in operating profit		$ 37		$ 27	$ 75	$ 52
Weighted-average assumptions used to determine net cost:
Discount rate used to measure service cost					3.90%	4.40%
Discount rate used to measure interest cost					3.30%	3.30%
Expected return on plan assets (as a percent)					7.50%	7.50%
Rate of compensation increase (as a percent)					4.00%	4.00%